Embodiments of the present invention relate generally to power system enclosures, and, more particularly, to a corrugated enclosure that includes vibration stabilizers thereon to reduce the vibration of cooling fins of the enclosure during transport.
Transformers, and similar devices, come in many different shapes and sizes for many different applications and uses. Fundamentally, all of these devices include at least one primary winding(s) with at least one core path(s) and at least one secondary winding(s) wrapped around the core(s). When a varying current (input) is passed through the primary winding a magnetic field is created which induces a varying magnetic flux in the core. The core is typically a highly magnetically permeable material which provides a path for this magnetic flux to pass through the secondary winding thereby inducing a voltage on the secondary (output) of the device.
Power transformers are employed within power distribution systems in order to transform voltage to a desired level and are sized by the current requirements of their connected load. If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit, through the transformer, to the load. Transformers are designated by their power rating, typically in kVA, which describes the amount of energy per second that they can transfer and also by their primary and secondary operating voltages, typically in kV. Medium power transformers can be rated up to 10,000 kVA and up to 46 kV while large power transformers can be rated up to 120,000 kVA and up to 345 kV.
One shortcoming of existing transformers is their susceptibility to operational problems associated with high temperatures of operation, both internal and external to the transformer. The largest source of heat in a transformer is heat created by the load current flowing through windings of the core-winding assembly, based on the inherent resistance of the wire from which the windings are constructed. High temperatures for long periods of time in transformers will destroy insulation positioned about and between the windings, thereby leading to a transformer failure. During the design of power transformers, considerable effort is spent to: reduce losses so as to decrease the generation of heat in the windings; move heat away from the windings (i.e., provide cooling) and spread the heat out by physical design (i.e., provide heat dissipation); and improve the winding insulation so that it can withstand greater exposure to heat.
With regard to providing cooling to the transformer windings and heat dissipation from the transformer, one common solution is to construct the transformer as a liquid-filled transformer. In a typical liquid-filled power transformer, a bath of dielectric insulating liquid is contained within the enclosure/tank of the transformer, with the core and windings of the transformer being submerged in the dielectric insulating liquid. Moving heat away from the windings is accomplished by direct contact of the windings with the dielectric insulating liquid. The denser the dielectric insulating liquid the better the heat transfer and, as such, the typical liquids used are selected both for their dielectric properties (insulating the high voltage) as well as their heat transfer properties.
In operation of a liquid-filled transformer, it is recognized that as heat is moved away from the windings and transferred to the dielectric fluid, a heat-exchanging mechanism for dissipating heat in the dielectric fluid is required. One existing type of heat-exchanging mechanism that is typically utilized is a bank of corrugate that is attached to the enclosure. The enclosure is constructed to include a corrugate bank on one or more sides thereof—with each corrugate bank being formed from a plurality of cooling fins. The cooling fins provide the dielectric insulating liquid a path to circulate through a region of increased surface area for the purpose of liquid-to-air heat exchange to cool the dielectric insulating liquid. The cooling fins, through convection, move the hot liquid through a channel formed in each fin, therefore providing more surface area for the air outside of the enclosure to contact the cooling fins to remove heat from the liquid.
While the corrugated enclosure functions to provide effective cooling for the transformer during operation, it is recognized that the structure of the enclosure provides challenges with respect to shipping and delivery of the enclosure to an end-use site. That is, during shipping of the enclosure, shipping vibrations and wind loads on the corrugate bank may lead to cracks at a weld between a cross-rod that runs along the length of the corrugate bank and lead to cracks where the respective cooling fins are joined to the enclosure tank—i.e., a “triple point.”
To address these shipping vibrations present in the corrugated enclosure, stabilizer rods have been utilized in order to minimize such vibrations. One existing use of such stabilizer rods includes placement of a single ¼ inch stabilizer rod at each of the corners of the corrugate bank, with the stabilizer rod extending out from the tank wall and being joined to the corrugate cross-rod at a location between the two outermost fins of the corrugate bank. While these single stabilizer rods are effective in preventing cracks at a weld between the corrugate cross-rod and respective cooling fins, the stabilizer rods undesirably channel more forces down the outermost cooling fin—which can lead to leaks at the base of that fin where it joins to the tank. In addition, long cross country trips with a long vibration duration can lead to leaks at the cross-rod and corrugate cooling fin.
Therefore, it would be desirable to provide a vibration stabilizer that reduces the level of vibration of cooling fins of a corrugate enclosure during transport. Such a vibration stabilizer would reduce the effect of vibration on the welds between the cross-rod and the cooling fins, while also reducing the amount of force channeled down the outermost cooling fins, so as to prevent leaks at the base of an outermost fin where it joins to the tank.